To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
in addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
in a typical wireless communication system, terminals positioned in areas with poor signal quality, such as cell boundaries or shadow areas, are difficult to serve with seamless communication services from base stations.
To address this issue, more attention is paid to relay networks that bring up with expanded service coverage and increased system capacity. A relay network means a network that expands service coverage with relay nodes. A relay node receives signals from a source node and transfers the received signals to other relay node or a destination node. The technique in which a relay node relays signals between a source node and other relay node or a destination node is denoted a “multi-hop transmission.”
A representative relay network-related technique is IEEE 802.15.3-based wireless personal area network (WPAN).
Various schemes are being prepared to equip relay network with increased network capacity, reduced channel usage count along with steady communication performance.
Among such relay network-related schemes, noisy network coding has been proposed to obtain a communication performance that approaches the channel capacity. Noisy network coding is among the schemes for utilizing relay nodes in a relay network.
According to this scheme, a relay node in a relay network receives analog signals from a source node, quantizes the received analog signal, converts into digital signals, channel-codes, and transmits the resultant signals to a next node.
The noisy network coding scheme keeps the gap between a theoretical channel capacity achievable from a relay network and the upper-bound channel capacity at a predetermined value.
Upon adopting the noisy network coding scheme, the relay node conducts two stages of computation in order to transfer received signals to a next node. The first stage is to quantize the signals received from the source node, and the second is to map the quantized signals to particular symbols and transmit the mapped signals to the next node. For example, the next node is an other relay node or a destination node.
The relay node, upon the second stage of computation, conducts channel coding on the quantized signals. A low density generator matrix (LDGM) or LDPC code comes in use for the channel coding.
The following documents are related to the channel coding performed by the relay node.
[1] “Coding and System Design for Quantize-Map-and-Forward Relaying,” IEEE Journal on Selected Areas in Communications, V. Nagpal, et al, 11, Nov. 2013, 1423-1435
[2] “Graph-based Codes for Quantize-Map-and-Forward Relaying,” IEEE information Theory Workshop, A. Sengupta, et al, 16-20, Oct. 2011, 140-144
[3] “Turbo-Like Codes for Transmission of Correlated Sources over Noisy Channels,” IEEE Signal Processing magazine, Garcia-Frias J., et al, September 2007, 58-66
[4] “Compression of Correlated Binary Sources Using Turbo Codes,” IEEE Communications Letters, Garcia-Frias J., et al, October 2001, 417-419
Document [1] supra proposes the optimization of channel codes used in transmitting nodes and relay nodes. Pursuant to Document [1], there is a single relay node; the destination node uses multiple antennas; and the source node and relay node adopt the diagonal-bell laboratory layered space-time (D-BLAST) scheme for signal transmission. The optimization set forth in Document [1] applies to the receiving node independently observing signals respectively transmitted from the source node and the relay node. In other words, this scheme is difficult to apply to general relay networks.
Document [2] discloses selecting the best performing component code through repetitive simulations and allowing the relay node to use the same. Document [2], however, fails to suggest a generalized design to put the best performing component code to use.
Document [3] concerns use of LDGM codes to maintain the correlation between information items respectively observed by terminals, The technique set forth in Document [3] makes use of LDGM codes, in parallel or in a sequential and consecutive way, in order to address the high error floor issue that arises due to the low order of LDGM matrix.
Document [4] bears similar research results to those of Document [3]. Document [4] discloses using convolutional codes that are in parallel or sequentially consecutive with each other. Use of such distributed turbo codes (turbo-like codes) causes the joint decoding by the destination node to be too complicated, and in some cases, cannot guarantee the optimized relay network.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.